Eduard Shevardnadze, who has died aged 86, deserves to go down in history as one of the major figures of our age for steering the Soviet Union in from the cold during his five and a half years as Mikhail Gorbachev's foreign minister, from 1985 onwards. After the end of the Soviet Union, he became the leader of his native Georgia, now an independent country, and took a brave stand. In the autumn of 1993, he stood in the middle of a brutal battle in Sukhumi in an effort to defend Georgia's sovereignty against Abkhazian separatists. However, his good name was later tarnished amid allegations of corruption involving him and his family.

As Soviet foreign minister he had established a close working partnership with the US and its western allies, and gave meaning and substance to perestroika, the principle of restructuring. He probably understood far earlier than Gorbachev that perestroika, once unleashed, could not be used merely to dabble with reform of the communist system. He grasped that perestroika was the engine of fundamental change at home and abroad. When the time came, he was able to shed the communist credo and to embrace the prospect of democracy. And in 1990, when Shevardnadze realised that Gorbachev was too conservative to make the intellectual leap away from communism, he jumped ship, gave up his beloved foreign ministry and eventually left the party.

It was Shevardnadze's mischance to have been born in Georgia. Had he been Russian, he would certainly have remained in Moscow after the breakup of the Soviet Union, and would have become a significant force in Russian politics. As it was, he had to leave the field to Boris Yeltsin, and in 1992, returned, disillusioned, to the Georgian capital, Tblisi, having decided it was his unpalatable duty to try to end the economic and political chaos in his country.

Shevardnadze, the son of Ambrosi, a teacher, and Sophio (nee Pateishvili), grew up in the rural community of Mamati near the Black Sea and, eschewing his parents' hopes that he would be a doctor, began his political life at the age of 20 as a Communist party apparatchik. He eventually rose to become first secretary and party boss in his state. There were glimmers of enlightenment even during those years: he railed against Georgia's inbred corruption and introduced mildly reformist economic policies, which significantly raised the republic's prosperity – bringing him to Gorbachev's attention in Moscow.

But Gorbachev's decision to name Shevardnadze foreign minister came as a complete surprise both inside and outside the Soviet Union. He was virtually unknown in the west and the appointment was thought to signify that Gorbachev meant to retain personal charge of foreign policy. It may have started that way, but before long it turned into a partnership of equals – indeed only historians will be able to tell which of them was the greater innovator in the drive for "new thinking".

Towards the end, Shevardnadze had probably become the more visionary of the two. After his arrival at the foreign ministry, Shevardnadze surprised even himself when he quickly developed a grasp of foreign and security issues. He also brought in a new breed of Soviet diplomats, which eased the way when negotiating with foreign leaders.

After decades of confrontation with the unbending, sharp-tongued Andrei Gromyko, the new Soviet foreign minister would, anyhow, have brought relief to other players on the international stage. He was not a Mr Niet, and he won many friends. A man of small build, with a whiff of white hair and an easy smile, he may have lacked the Gorbachovian charisma, but he more than made up for it with charm, warmth, humour and acute intellect.

"Civilised person-to-person relations are above ideology or class or particular interests," he told the Guardian in 1990, during the negotiations on German reunification. "This is what guides me when I talk to James Baker [the then US Secretary of State], or to Douglas Hurd, or Hans-Dietrich Genscher. They are partners, people with whom I have been able to establish a good relationship." Shevardnadze was unperturbed about depicting western politicians as friends, even if domestic critics in the Soviet Union criticised him for it.

In December 1989, Gorbachev had solemnly declared at the Malta summit with President George Bush Sr that "the Soviet Union no longer regards the United States as an enemy".

"This is a great phrase that can shape our relations with all western countries," Shevardnadze stressed. Among other advantages, it meant that negotiations could be conducted on a basis of frank speaking and give and take. "We don't waste time on unnecessary things. We say what we think. If we can agree, that's fine. If we can't, then we postpone the discussion. But we no longer try to deceive each other and are establishing a new network of foreign policy relations."

Before Gorbachev, Shevardnadze had understood that the logic of their foreign policy, with its aim of ending east-west confrontation and reversing the arms race, must inevitably lead to the breakup of the Soviet bloc and to German reunification. Against domestic opposition, he insisted on negotiating the "two plus four" German reunification treaty, between the two German governments and the four former allied powers: the US, the UK, France and the Soviet Union. In the process, he made enemies among the Soviet military, which cost him dearly when he sought its help, largely in vain, during his struggles against rebellion in Georgia.

Shevardnadze caused consternation abroad when he resigned as foreign minister in December 1990, not least because he explained his decision as an attempt to shock Gorbachev into the realisation that "dictatorship is advancing" and that the conservative revisionists had to be resisted. Later he admitted that he had begun to doubt Gorbachev's own good faith. The friendship was at an end.

A few months later, Shevardnadze became the first major Soviet figure to resign from the Communist party, increasingly alienated from it and disillusioned. He dabbled in creating new, democratic political formations, though in November 1991 reluctantly accepted Gorbachev's pressing invitation to prop up the dying regime by returning to the foreign ministry. But his heart was not in it. He could see the inevitability of a coup, the breakup of the Soviet Union, the end of his political influence in Moscow.

In 1992 he was made speaker of the Georgian parliament and became the country's leader. It was a poisoned chalice and he knew it. With characteristic courage, he fought tenaciously to restore order and economic prosperity, and in 1995 survived a car bomb explosion outside the parliament building, as he went to sign a new constitution that was to bring four years of civil war to an end. He was then elected president.

On 23 November 2003, after the Rose Revolution street protests about disputed election results, he was forced to resign, amid allegations of electoral corruption. Ultimately, Shevardnadze could not hide his disappointment and his sense of failure both in Georgia, and also in the collapse of the dreams for a brave new world throughout the territory of the former Soviet Union.

His wife Nanuli Tsagareishvili, whom he married in 1950, died in 2004. They had a son and a daughter.

•Eduard Shevardnadze, politician, born 25 January 1928; died 7 July 2014